The invention generally relates to improved medical devices, systems, and methods. In many embodiments, the invention provides devices, systems, and methods for heart rhythm management. In some specific embodiments, a heart stimulation device and/or system (e.g., including an epicardial pacemaker, implantable cardioverter-defibrillator (ICD), or the like) is provided for managing the heart rhythm of a patient. In these or other embodiments, delivery devices and kits can be provided for delivering implantable devices to an attachment location in the pericardial space of a patient. In further aspects, recapture devices are provided for detaching, repositioning and/or removing implants from a patient. Some cardiac rhythm devices, systems, and methods described herein include a heart-surface mounted stimulation device (including a stimulation signal generator) and an activity sensor that can be mounted away from the heart. Methods are also provided for delivering, implanting, repositioning, and/or retrieving implantable devices to or from an implantation site in the pericardial space of a patient. Still further aspects of the invention are described herein below.
An implantable cardioverter-defibrillator (ICD) is an implanted device that combines the functionality of a cardioverter and a defibrillator into a single implantable device. Specifically, the ICD may monitor the rate and rhythm of the heart and may deliver electrical shocks to the heart when the monitored heart rate exceeds a desired heart rate. Additionally, the ICD may deliver electrical energy to the heart to during cardiac dysrhythmias, ventricular fibrillation, and pulseless ventricular tachycardia to depolarize a mass of the heart muscle to terminate the dysrhythmia. Artificial implantable pacemakers are devices that are configured to maintain a desired heart rate of a patient with a naturally slower heart rate. Some artificial pacemakers may include the functionality of a defibrillator as well. Recently, left-ventricular cardiac pacing has been practiced to ameliorate heart failure; a practice termed cardiac resynchronization therapy (CRT). CRT has been practiced with electrode-leads and a pulse generator, either an implantable cardioverter-defibrillator (CRT-D) or an otherwise conventional pacemaker (CRT-P). The left-ventricular pacing conventionally uses an electrode in contact with cardiac muscle in that chamber. The corresponding electrode-lead is usually placed endocardially in a transvenous manner through the coronary sinus vein, or epicardially.
ICDs and pacemakers often include a housing (generally containing circuitry, a power source, and the like) implanted by in a small pocket created under the left collar bone. Leads typically extend from a connector between the lead and the housing, through a vein, along the blood flow path of the cardiovascular system into the heart, and to an electrode attached to heart tissues within one or more chambers of the heart. The implantation procedures may require not only transvenous delivery of the leads to the one or more heart chambers, but the leads may also extend through one or more valves of the heart, so that the valves open and close around the leads. The advancement and placement of the leads is often performed under fluoroscopic guidance to provide a physician a view of a stimulation position of the electrode lead. To facilitate fluoroscopic guidance, contrast agents may be introduced into the blood of the patient. Once implanted and attached, the pacemaker may pace the chambers and may also sense the heart's natural rhythm.
Recently, leadless pacemakers have been developed. These leadless pacemakers are self-contained intracardial pacemaker systems in which an electrode is rigidly affixed to the housing containing the signal generating circuitry and the like, so that the leadless pacemaker is implanted in a chamber of the heart and can operate without the use of flexible transvenous leads, obviating the need of creating a surgical pocket for implanting the pacemaker and thereby avoids visual lumps associated with subclavical implantation of pacemakers.
While the new leadless pacemakers represent advances in heart rhythm management for many patients, work in connection with the present invention suggests that further improvements may be available. For example, intracardiac pacemakers are often small enough to traverse veins of the patient and to fit within the chambers of the heart. Unfortunately, the reduced size may restrict battery capacity for the implanted device and may thus unduly limit pacemaker life. Further, given the delivery and implantation of standard pacemakers or the new leadless pacemakers at least partially within the blood flow of the patient, an associated risk of thrombus formation may remain, along with associated risks of clot debris traveling in the blood to the brain, heart, or lungs—thereby presenting at least some risk of stroke, myocardial infarctions, and/or pulmonary embolisms. Because of the risk associated with thrombus, it may not be safe to place the leads and leadless pacemaker in the left heart (e.g., left atrium and left ventricle) which presents serious limitations for efficacy treatment (e.g., bi-ventricular pacing or three-chamber pacing). In addition, both leads and leadless pacemakers are associated with perforation of the right atrium or right ventricular walls, which could occur during placement of the lead or leadless pacemaker over time. The risk of perforation is associated with serious clinical sequel or death. Moreover, it may be desirable to further simplify implantation methods, particularly when implantation involves test pacing of a candidate stimulation site, sensing thresholds, repositioning of the electrodes, etc., prior to identifying a preferred attachment location, ideally without having to re-anchor and remove the housing for each unsuccessful candidate location. Additionally, there may be some risk that intracardiac devices become dislodged during their lifetime given the constant motion of the heart, and it would be best if the resulting risks could be mitigated.